<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#separator {
 height: 20px;
 background-color: green;
}
#parent {
 background-color: green;
 margin-top: 90px;
}
#first-child {
 margin-top: -40px;
 margin-bottom: -60px;
}
#last-child {
 height: 20px;
}
</style>
</head>
<body>
<div id="separator"></div>
<div id="parent">
 <div id="first-child"></div>
 <div id="last-child"></div>
</div>
</body>
</html>
